This is only the beginning. Each chip is loaded with vastly different details of how to actually program its flash memory. Sure, they're both "flash", but just because they're called the same and use basically the same physical semiconductor process to store non-volatile data doesn't mean these different vendors did anything else similarly.

At least for access to RAM, they both do have the AHB-AP component. At least that part comes from ARM, so it's likely to be the same.

But even then, many thorny details can get in the way. For example, in the Freescale chip you can access the MDM-AP and even the AHB-AP while the chip is in reset mode. But Freescale's bus matrix obeys the reset and won't work at all. So if you want to get to anything that can't be reached directly inside the ARM core or through the core's private peripheral bus, you have to go through quite a lot of work to configure the debug unit to catch the reset vector and put the chip into halt mode before it can start, just to be able to release reset and gain access to everything else (like the RAM) which lies on the other side of that bus matrix.

I honestly haven't fiddled with Atmel's ARM chips much. But years ago I did play with the NXP LPC2000 ones (long before NXP acquired Freescale, both of whom are about to be acquired by Qualcomm). The LPC chips were riddled with other gotchas. One particularly difficult problem was they put the GPIO onto the AHB to avoid the high latency in whatever bus bridge they were using back then, but they added some (undocumented) bug where it wouldn't properly ignore bus cycles during debug mode. At the time I found an ugly workaround, but didn't continue farther with those chips since Freescale was soon to release the first ones with DSP extension and a good DMA controller.

Probably very few people outside of IAR, Segger and maybe the OpenOCD devs ever know of these internal chip issues....

This thread is on STAR Otto and started in 5/2016. It seems to be sure that this will never be available.

That might be the case... Just dropping in for a 3 monthly update. If indeed Otto was "about to be on sale", I think that is kicked into the long grass, by the recent hostile re-splitting of the amicable merger of the warring split Arduinos. If arduino.cc are not committing to Due, it seems unlikely they will commit to Otto. The Otto was a "pet project" of one of the devs at arduino.org, so that is probably the end of that. RIP, next to Tre.

Anyway, I agree with Paul, if the Otto did get launched now, Cortex M4 is looking a bit tame. I expect there to be some low end Cortex M7s around, if not already (market moves too fast for me to keep up!).

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